Locking Polyaxial Ball And Socket Fastener

ABSTRACT

A polyaxial ball and socket joint that can be locked into a fixed position. The fastening system consists of the polyaxial ball and socket joint used in conjunction with a bone screw having threads on one end for use in anchoring to the spine and a spherical connector on the other end operating as a pivot point about which a connecting assembly moves in a polyaxial fashion. A substantially U-shaped connecting assembly has a lower receptacle that operates as a socket for housing an upper retainer ring and a lower split retaining ring. The socket is receptive to the spherical connector which is inserted through the lower split retainer ring causing a momentary displacement thereof which allows for the positioning of the spherical connector between the upper and lower retainer rings.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S.Provisional Patent Application No. 61/114,515 filed on Nov. 14, 2008,the contents of which are herein incorporated by reference.

FIELD OF THE INVENTION

This invention is directed to the field of ball and socket fasteners,and in particular to a polyaxial ball and socket fastener adapted foruse as a spinal implant.

BACKGROUND OF THE INVENTION

There are numerous ball and socket fasteners, however, when theapplication is applied to a particular product, the ball and socket mustmeet minimum specifications in order to be effective. For instance, inthe field of spinal pathologies, the development of spinal fixationdevices represents a major medical breakthrough. Surgically implantedfixation systems are commonly used to correct a variety of backstructure problems, including those which occur as a result of trauma orimproper development during growth. A commonly applied fixation systemincludes the use of one or more stabilizing rods aligned in a desiredorientation with respect to a patient's spine. Anchoring screws areinserted into the patient's spinal bones, and a series of connectors areused to rigidly link the rods and anchors.

A variety of designs exist, with each design addressing various aspectsof the difficulties that arise when one re-shapes an individual's spineto follow a preferred curvature. Known spinal implant systems oftencorrect one set of problems only to create new ones.

Common to all spinal implant systems is the necessity for properanchoring to the bone so as to provide support for the aforementionedcomponents. While bone screws are commonly used for anchoring, the useof a polyaxial design has proven very effective in allowing a surgeonthe flexibility to secure an installation with minimal strain on theindividual.

For this and other reasons, screws located in bone structure typicallyuse a polyaxial base and a specially designed connector member forattachment to a component such as an alignment rod. A problem with thecurrent technology is that bone structure cannot be determined until thepatient's bone is exposed. This problem requires a large inventory ofvarious sized implants to be on hand during every surgery. The surgeonmust search through the inventory to assembly a combination based on hisprediction of what will be required. Even if an implant combination ispredicted, the anchoring screw may still require angular insertion dueto muscle structure or nerve locations. Any movement of muscle and othertissue increases the difficulty of the operation and can be a majortrauma to the patient. Still yet, bone condition may require oversizethreads to achieve a suitable purchase to the bone. As a consequence,the surgeon must either maintain a large inventory of anchoring devices,or have a vendor standing by with a large inventory of anchoring devicesthat will hopefully meet the individual requirements.

A conventional polyaxial bone screw typically consists of a single shaftwith a coarse thread at one end for threading into the bone. A sphericalball is positioned at an opposite end for coupling to a connectingmember. For example, a number of patents exist for bone screw anchoringassemblies that include a U-shaped connector element which acts as asaddle for attachment to an alignment rod. U.S. Pat. No. 5,133,717 setsforth a sacral screw with a saddle support. Disclosed is the use of anauxiliary angled screw to provide the necessary support in placing thescrew in an angular position for improved anchoring.

U.S. Pat. No. 5,129,900 sets forth an attachment screw and connectormember that is adjustably fastened to an alignment rod. An oblong areaprovided within each connector member allows minute displacement of thealignment rod.

U.S. Pat. No. 4,887,595 discloses a screw that has a first externallythreaded portion for engagement with the bone and a second externallythreaded portion for engagement with a locking nut. The disclosureillustrates the use of a singular fixed shaft.

U.S. Pat. No. 4,946,458 discloses a screw which employs a sphericalportion which is adapted to receive a locking pin so as to allow oneportion of the screw to rotate around the spherical portion. A problemwith the screw is the need for the locking pin and the inability of thebase screw to accommodate a threaded extension bolt.

U.S. Pat. No. 5,002,542 discloses a screw clamp wherein two horizontallydisposed sections are adapted to receive the head of a pedicle screw foruse in combination with a hook which holds a support rod at anadjustable distance.

U.S. Pat. No. 4,854,304 discloses the use of a screw with a top portionthat is adaptable for use with a specially designed alignment rod topermit compression as well as distraction.

U.S. Pat. No. 4,887,596 discloses a pedicle screw for use in coupling analignment rod to the spine wherein the screw includes a clamp permittingadjustment of the angle between the alignment rod and the screw.

U.S. Pat. No. 4,836,196 discloses a screw with an upper portion designedfor threadingly engaging a semi-spherical cup for use with a speciallydesigned alignment rod. The alignment rod includes spaced apartcovertures for receipt of a spherical disc allowing a support rod to beplaced at angular positions.

U.S. Pat. No. 5,800,435 sets forth a modular spinal plate assembly foruse with polyaxial pedicle screw implant devices. The device includescompressible components that cooperatively lock the device alongincluded rails.

U.S. Pat. No. 5,591,166 discloses an orthopedic bone bolt and bone plateconstruction including a bone plate member and a collection offasteners. At least one of the fasteners allows for multi-angle mountingconfigurations. The fasteners also include threaded portions configuredto engage a patient's bone tissue.

U.S. Pat. No. 5,569,247 discloses a multi-angle fastener usable forconnecting patient bone to other surgical implant components. The '247device includes fastening bolts having spherical, multi-piece heads thatallow for adjustment during installation of the device.

U.S. Pat. No. 5,716,357 discloses a spinal treatment and long bonefixation apparatus. The apparatus includes link members adapted toengage patient vertebrae. The link members may be attached in achain-like fashion to connect bones in a non-linear arrangement. Theapparatus also includes at least one multi-directional attachment memberfor joining the link members. This allows the apparatus to be used informing a spinal implant fixation system.

Another type of spinal fixation system includes rigid screws that engagethe posterior region of a patient's spine. The screws are designed withrod-engaging free ends to engage a support rod that has been formed intoa desired spine-curvature-correcting orientation. Clamping members areoften used to lock the rod in place with respect to the screws. Insteadof clamping members, other fixation systems, such as that disclosed inU.S. Pat. No. 5,129,900, employ connectors that join the support rodsand anchoring screws. The connectors eliminate unwanted relative motionbetween the rod and the screws, thereby maintaining the patient's spinein a corrected orientation.

Other spinal fixation systems employ adjustable components. For example,U.S. Pat. No. 5,549,608 includes anchoring screws that have pivotingfree ends which attach to discrete rod-engaging couplers. As a result,the relative position of the anchoring screws and rods may be adjustedto achieve a proper fit, even after the screw has been anchored into apatient's spinal bone. This type of fixation system succeeds in easingthe rod-and-screw-linking process. This adjustment capability allows thescrews to accommodate several rod paths.

U.S. Pat. No. 7,445,627 discloses a fastener and a bone fixationassembly for internal fixation of vertebral bodies. According to oneexemplary embodiment, a tulip assembly is employed, the tulip assemblyincludes a non-circular surface disposed on its outer surface. Afastener is coupled to the tulip assembly and positionable to retain thetulip assembly on the head of a screw. A cap having an outer surface anda plurality of inner protrusions mateably connects to the non-circularsurface on the tulip body to compress the tulip assembly to secure arod.

U.S. Publication No. 2008/0177322 discloses a spinal stabilizationsystem that includes bone fastener assemblies that are coupled tovertebrae. Each bone fastener assembly includes a bone fastener and acollar. The bone fastener has a head portion having at least a firstcross-sectional shape in a first plane, and a second cross-sectionalshape in a second plane. The collar has a circular opening in thebottom, with a relief extending from the circular opening. The secondcross-sectional shape of the bone fastener is keyed to the opening topermit insertion of the bone fastener into the collar assembly from thebottom. After insertion, the bone fastener is rotated to prohibitremoval of the bone fastener from the collar. The collar can then berotated and/or angulated relative to the bone fastener. An elongatedmember can be positioned in the collar and a closure member is then usedto secure the elongated member to the collar.

U.S. Publication No. 2006/0241599 discloses a polyaxial fixation devicehaving a shank with a spherical head formed on a proximal end thereof,and a receiver member having an axial passage formed therein that isadapted to polyaxially seat the spherical head of the shank. Thepolyaxial bone screw further includes an engagement member that isadapted to provide sufficient friction between the spherical head andthe receiver member to enable the shank to be maintained in a desiredangular orientation before locking the spherical head within thereceiver member.

U.S. Publication No. 2006/0235392 discloses a system for connecting afastener element (e.g., a pedicle screw) relative to a rod for thepurposes of vertebral fixation. The system may permit multi-axialmovement between the fastener element and the rod. Further, the systemmay permit the angular relationship between the fastener element and therod to be held in a desired orientation.

U.S. Publication No. 2006/0155277 discloses an anchoring element forsecuring a rod on a vertebra, that comprises a retaining means forreceiving the rod, a safety element placed on the retaining means, asecuring element which can be placed on the body of the vertebra, and aclamping device which is arranged between the retaining means and thesecuring element. The clamping device includes a ring-shaped mount, apartially conical-segment shaped bearing and an intermediate elementwhich is embedded in the mount and which engages the bearing, wherebythe mounting is moveable in a removed state in relation to the bearing,whereas the mount is maintained in a clamped state on the bearing bymeans of the intermediate element. The mount is rigidly connected to theretaining means and the bearing is rigidly connected to the securingelement.

U.S. Publication No. 2006/0149240 discloses a polyaxial bone screwassembly that includes a threaded shank body having an upper capturestructure, a head and a multi-piece retainer, articulation structure.The geometry of the retainer structure pieces correspond and cooperatewith the external geometry of the capture structure to frictionallyenvelope the retainer structure between the capture structure and aninternal surface defining a cavity of the head. The head has a U-shapedcradle defining a channel for receiving a spinal fixation orstabilization longitudinal connecting member. The head channelcommunicates with the cavity and further with a restrictive opening thatreceives retainer pieces and the capture structure into the head butprevents passage of frictionally engaged retainer and capture structuresout of the head. The retainer structure includes a substantiallyspherical surface that mates with the internal surface of the head,providing a ball joint, enabling the head to be disposed at an anglerelative to the shank body.

U.S. Pat. No. 6,716,214 discloses a polyaxial bone screw having a boneimplantable shank, a head and a retaining ring. The retaining ringincludes an outer partial hemispherical surface and an inner bore withradially extending channels and partial capture recesses. The shankincludes a bone implantable body with an external helical wound threadand an upwardly extending capture structure. The capture structureincludes at least one spline which extends radially outward and has awedged surface that faces radially outward therefrom. The capturestructure operably passes through a central bore of the retaining ringwhile the spline passes through a suitably shaped channel so that thespline becomes positioned above the head, at which time the shank isrotated appropriately and the shank is drawn back downwardly so that thespline engages and seats in the capture recess. The head includes aninternal cavity having a spherical shaped surface that mates with thering surface and has a lower restrictive neck that prevents passage ofthe ring once the ring is seated in the cavity.

U.S. Pat. No. 6,565,567 discloses a pedicle screw assembly for use witha rod for the immobilization of bone segments. The assembly is comprisedof a screw, a polyaxial housing for receiving the screw, a washer, a setscrew, and a cup-shaped cap. The lower portion of the housing terminatesin a reduced cross-sectional area, which engages the bottom of the screwhead. When the screw is placed inside the polyaxial housing and thescrew is secured into the bone, the polyaxial housing is pivotable withthree degrees of freedom. The housing includes a top portion with a pairof upstanding internally threaded posts. A washer is inserted betweenthe head of the screw and the rod. A cap, having a bottom, with a pairof posts accommodating openings and a lateral cross connector, is placedover the posts so that the cross connector engages the rod. The crossconnector and washer have concave generally semi-cylindrical rodengaging surfaces to prevent the rod from rotating or sliding within thehousing once the set screw is tightened. A set screw is threaded intothe housing posts to secure the rod within the housing. The washer has aroughened lower surface which, in conjunction with the reducedcross-sectional area at the bottom of the housing, securely clamps andlocks the housing to the screw head when the set screw is tightened.

U.S. Pat. No. 5,501,684 discloses an osteosynthetic fixation devicewhich consists of a fixation element which has a conical head sectionand an anchoring element abutting it which is for attachment into thebone. The fixation device also consists of a spherically formed,layered, slotted clamping piece which has a conical borehole forinstallation of the conical head section, and which is meant for lockingwithin a connecting piece equipped with a spherically shaped layeredborehole. Fixation piece has an axially arrayed tension element,permitting axial displacement and wedging of conical head section in theborehole that corresponds with it. The fixation device is appropriatefor use as a plate/screw system, an internal or external fixator, and inparticular for spinal column fixation.

U.S. Pat. No. 4,693,240 discloses a bone pin clamp for external fracturefixation. The apparatus comprises rotation, slide and housing elementsnested one within the next, each such element having an aperture toreceive a pin therethrough, and the rotation and slide elementsrespectively affording pin adjustment in azimuth and zenith, and inheight, relative to the housing element. A locking mechanism including acommon actuator member is operable simultaneously to lock the pin androtation and slide elements in the housing element. In a preferred form,the housing element serves as a cylinder with the slide element as akeyed piston therein, and the rotation element is a disc located betweena screw and annular thrust members engaged in the piston, the piston anddisc being split respectively to lock by expansion and compaction underscrew action towards the thrust members.

U.S. Pat. No. 4,483,334 discloses an external fixation device forholding bone segments in known relation to each other. The deviceincludes a pair of bone clamp assemblies each secured to bone pinsextending from the bone segments, a bridge extending between the pinclamp assemblies, and a specialized high friction universal assemblyconnecting the bridge to each of the pin clamp assemblies.

U.S. Pat. No. 4,273,116 discloses an external fixation device forreducing fractures and realigning bones that includes sliding universalarticulated couplings for enabling easy adjustment and subsequentlocking of connections between Steinmann pins and tubular tie-rods. Thecouplings each include a split, spherical adapter sleeve which isembraced by the matching inner surface of an open ring portion of acoupling locking clamp having clamp lugs tightenable against a block bymeans of a nut-and-bolt assembly. Further nut-and-bolt assemblies aredisposed in elongated slots in the blocks and cooperate with associatedclamping members to clamp the Steinmann pins to the blocks afteradjustment in two orthogonal directions and optional resilient bendingof the pins.

U.S. Pat. No. 6,672,788 discloses a ball and socket joint incorporatinga detent mechanism that provides positive biasing toward a desiredposition. The ball and socket joint can be used in flexible supportsthat hold and support items such as lamps, tools and faucets. The detentmechanism comprises two corresponding parts, one in the ball portion andthe second in the socket portion of the joint. The first detent part isa protrusion of some type and the second detent part is a groove orindentation that is adapted to accept and engage the protrusion. If theball contains the detent protrusion, then the socket contains the detentindentation. And conversely, if the socket contains the detentprotrusion, then the ball contains the detent indentation. The detenttensioning force can be provided by a spring or a spring band, thecharacteristics of the material from which the joint is made, or by someother similar tensioning device.

U.S. Publication No. 2003/0118395 discloses a ball and socket joint,which has a housing, a ball pivot mounted pivotably in the housing, anda sealing bellows, which is fastened to the housing and is mounted onthe ball pivot slidably via a sealing ring provided with two legs. Afirst leg of the two legs is in contact with the ball pivot undertension and the second leg meshes with the wall of the sealing bellows.The second leg is, furthermore, fastened in an anchoring ring arrangedat least partially in the wall of the sealing bellows.

U.S. Pat. No. 4,708,510 discloses a ball joint coupling assembly thatpermits universal movement and positioning of an object with respect toa vertical support shaft. Quick release/lock action is provided by aball joint assembly having a housing in which a ball and piston aremovably coupled. The ball is captured between annular jaw portions ofthe housing and piston, with locking action being provided by grippingengagement of the piston jaw portion and the housing jaw portion. Theball member is gripped in line-contact, compressive engagement by theannular edges of the piston jaw and housing jaw on opposite sides of theball. The piston is constrained for axial movement within the housingwith locking engagement and release being effected by rotation of athreaded actuator shaft.

U.S. Pat. No. 3,433,510 discloses a swivel structure for rigidly joiningfirst and second parts together. A first member is connected to thefirst part and a second member is connected to the second part. Anintermediate hollow member interconnects the first and second memberstogether. An enlarged outer end portion is provided on the first memberand includes a plurality of locking means thereon. Means are provided onthe second member for engaging one of the locking means. Means areprovided for threadably joining the hollow member and the second membertogether. A slot is provided in the hollow member and includes anenlarged entrance which passes the enlarged outer end portion and whichalso includes a restricted opening opposite the threaded joining of thehollow member and the second member together. The portion surroundingthe restricted opening opposes the forces imparted against the outer endportion as the second member is threadably joined to the hollow portionand bears against the outer end portion.

U.S. Patent Publication No. 2008/0269809 discloses a bottom loadingpedicle screw assembly. The device includes a pedicle screw and aconnector member. The pedicle screw includes a threaded lower portionwhile the upper portion includes a groove sized to accept a clip member.The clip member includes a spherical outer surface. In operation theclip is placed within the groove and the assembly is pressed through theopening in the bottom of the connector member. While the device isbottom loading, the device will separate when the pedicle screw isaligned with the connector member. The construction of the clip memberallows the clip to collapse sufficiently to pass back through theopening when the screw is positioned in alignment with the connector,requiring the connection to bone be placed at an angle with respect tothe connector for proper operation.

Thus, what is needed is a lockable polyaxial ball and socket joint thatcan be adapted for use in a spinal fixation system that includes theadvantages of known devices, while addressing the shortcomings that theyexhibit. The system should allow component interchageability at point ofinstallation, thereby addressing a wide variety of spinal deformitieswith less components.

SUMMARY OF THE INVENTION

Briefly, the present invention is a polyaxial ball and socket jointcapable of snap together assembly and thereafter lockable into a fixedposition. Disclosed is an exemplary embodiment of the ball and socketfastening system adapted for use in a spinal fixation system forreshaping the spine of a patient. The fixation system includes thepolyaxial ball having a bone screw extending outwardly therefrom for usein anchoring to the spine and a connector member that includes a socketconstructed and arranged to accept the polyaxial ball. In the disclosedembodiment, the connector member is illustrated as a U-shaped connectormember having a lower receptacle that operates as a socket for housingan upper retainer ring and a lower split retaining ring. The socket isreceptive to the spherical connector which is inserted through anaperture in the bottom of the connector assembly where the sphericalpolyaxial ball contacts the lower split retainer ring causing amomentary displacement thereof, allowing the ring to contact a pluralityof ramps that are constructed and arranged to open the split ringallowing the ball to pass through the ring positioning of the sphericalconnector between the upper and lower retainer rings. A set screw or nutcan then be utilized to press the upper retaining ring into contact withthe ball while simultaneously causing the lower split ring to engage alower portion of the ball as it wedges between the ball and the innersurface of the connector member immobilizing the connection.

This construction facilitates the receipt of the spherical connectorinto the bottom of the connector member, eliminating the requirement ofinserting the screw and spherical connector through the top opening ofthe connector member. This construction also allows for the use of boneanchors that will not fit through the top opening of the connectormember. In addition, the use of the dual retainer rings allows for thecoupling of an anchor screw to a connector member during surgery,without the aid of tools. In this manner, during surgery a surgeon candetermine the most advantageous bone screw, hook or other type of boneconnection to match the most advantageous connecting assembly. The boneconnector is then coupled to the connector assembly by inserting orsnapping the spherical connector into the socket of the connectingassembly. In operation, the spherical connector is pushed past the lowerretainer ring whereby the ring snaps past the largest diameter of theconnector to prohibit removal of the connector while still allowingpolyaxial movement between the spherical ball and the connector member.Because of the flexibility and resilience of the split retention ring,the mating parts do not require fine tolerances and are economical tomanufacture. The system is modular, employing a collection of anchoringassemblies that are linked, via various connectors, tostrategically-arranged stabilizing rods.

The connector members are rigid structures adapted to link an associatedanchoring assembly with one of the stabilizing rods. The stabilizingrods may be rigid or dynamic members shaped to form aspine-curvature-correcting and/or immobilizing path. Attaching eachanchoring assembly, via connectors, to a stabilizing rod forces apatient's back into a surgeon-chosen shape. Stabilizing rods may be usedsingly, or in pairs, depending upon the type of correction required. Therods vary in size, but typically extend between at least two vertebrae.

Accordingly, it is an objective of the present invention to teach theuse of a lockable polyaxial ball and socket fastener.

It is another objective of the present invention to disclose the use ofa lockable polyaxial ball and socket fastener for use in a spinalstabilization system.

Another objective of the invention is to disclose the use of a lockablepolyaxial ball and socket system that is capable of securing variousanchors to various connector members so as to reduce the amount ofinventory required to meet a particular installation.

It is another objective of the present invention to provide a polyaxialbone screw assembly for a spinal fixation system that permits componentadjustment during installation, thereby enabling satisfactory correctionof a wide variety of spinal deformities.

It is an additional objective of the present invention to provide a bonescrew assembly that includes a split ring locking mechanism that issimple, strong and reliable.

It is yet another objective of the present invention to provide apolyaxial bone screw that can be coupled to a reciprocal connectingmember without tools.

It is yet another objective of the present invention to provide a spinalfixation system that require minimum tools for installing of an anchorand securing element.

Other objectives and advantages of this invention will become apparentfrom the following description taken in conjunction with theaccompanying drawings wherein are set forth, by way of illustration andexample, certain embodiments of this invention. The drawings constitutea part of this specification and include exemplary embodiments of thepresent invention and illustrate various objects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top perspective view of the ball and socket fastener appliedto a spinal fixation device;

FIG. 2 is a top perspective view of the ball and socket fastener withthe anchoring member illustrating the polyaxial cooperation between thespherical ball and the connector member;

FIG. 3 is a side view of the ball and socket fastener;

FIG. 4 is a partial section view of the ball and socket fastener;

FIG. 5 is a section view of the connector assembly;

FIG. 6 is a top section view of the connector assembly;

FIG. 7 is a perspective section view of the connector assembly takenalong lines 7-7 of FIG. 6;

FIG. 8 is a top perspective view of the connector assembly;

FIG. 9 is a top view of the connector assembly;

FIG. 10 is a section view of the connecter assembly taken along lines10-10 of FIG. 9;

FIG. 11 is a partial bottom perspective view of the connector member;

FIG. 12 is a partial top perspective view of the connector member;

FIG. 13 is a bottom view of the connector member;

FIG. 14 is a top perspective view of the seat portion of the connectormember;

FIG. 15 is a perspective view of the lower split retaining ring;

FIG. 16 is a perspective view illustrating the seat portion and thelower retaining ring;

FIG. 17 is a top perspective view of the upper retaining ring;

FIG. 18 is a lower perspective view of the upper retaining ring;

FIG. 19 is a perspective view illustrating assembly of the retainingassembly to the spherical connector;

FIG. 20A is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 20B is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 20C is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 20D is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 20E is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 20F is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 20G is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 20H is a side view illustrating assembly of the spherical ball andthe connector assembly;

FIG. 21A is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 21B is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 21C is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 21D is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 21E is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 21F is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 21G is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 21H is a section view illustrating assembly of the spherical balland the connector assembly;

FIG. 22 is a perspective view of an alternative embodiment of theinstant invention;

FIG. 23 is a partial side view of the embodiment illustrated in FIG. 22;

FIG. 24 is a top view of the embodiment illustrated in FIG. 22;

FIG. 25 is a perspective view of a retaining nut;

FIG. 26 is a perspective view of an alternative embodiment of theinstant invention having only mono-axial movement;

FIG. 27 is a front view of the bone anchor of the embodiment illustratedin FIG. 26;

FIG. 28 is a side view of the bone anchor of the embodiment illustratedin FIG. 26;

FIG. 29 is a partial perspective view of the spherical connectorutilized in the mono-axial embodiment;

FIG. 30 is a partial section view of the connector assembly utilized inthe mono-axial embodiment;

FIG. 31 is a lower perspective view of the upper retaining ring utilizedin the mono-axial embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

While the present invention is susceptible of embodiment in variousforms, there is shown in the drawings and will hereinafter be describeda presently preferred embodiment with the understanding that the presentdisclosure is to be considered an exemplification of the invention andis not intended to limit the invention to the specific embodimentsillustrated.

Referring generally to the Figures, disclosed is an exemplary embodimentof the locking polyaxial ball and socket fastening system adapted foruse in a spinal fixation system. The fastening system includes aspherical ball secured or formed integrally with a bone anchor andconnecting assembly that includes a snap-in type receptacle (38) for thespherical ball to form a polyaxial joint. The connector assembly alsoincludes a receiver that may be used in conjunction with a connectingrod member for securing at least two bone anchors together.

Referring to FIGS. 1-4 and 19, the bone anchor of the preferredembodiment is a bone screw (12) including a shank (14) having a lengthwith at least one helical thread (16) formed along the length thereof.It is important to note that the proportions of the bone screw depictedare for illustrative purposes only and variations in the length of theshank, diameter of the screw, thread pitch, thread length, number ofthread leads, shank induced compression and the like may be variedwithout departing from the scope of the invention. At the upper end (20)of the shank (14) is a ball shaped spherical connector (18) having apredetermined diameter (d) (FIG. 19). A driver receptacle (22) islocated along the upper end (20) of the spherical connector for use ininstalling the bone screw by use of driving tool. It should be notedthat the driving receptacle may be any shape, male or female, suitablefor cooperation with a driving tool to rotate the bone screw into itsfinal position.

Referring to FIGS. 1-16, the U-shaped connector assembly is illustrated.The U-shaped connector assembly (30) includes an upper connector member(31) (FIGS. 11-13), a lower connector member (33) (FIG. 14), an upperretaining ring 42 and a lower split retaining ring (40) (FIG. 5). Theupper connector member includes a substantially circular side wall (32)divided by a pair of U-shaped openings forming an upstanding first sidewall (34) and second side wall (36). The side walls preferably include aplurality of recessed flutes (90). The flutes are constructed andarranged to provide a gripping surface that cooperates with a tool (notshown) to allow a physician to apply a counter torque to the connectormember during tightening of the set screw (80)(FIG. 1). In addition tothe flutes a groove (91) is cut around the perimeter of the connectormember for attachment of an extender tube (not shown). Extender tubesare well known in the art of minimally invasive spinal procedures. Thelower surface of the upper connector assembly includes a plurality oframps (94) that are positioned to cooperate with the lower splitretaining ring (40) during assembly to open the split ring so that themajor diameter (d) (FIG. 19) of the spherical ball can pass through thering (see FIGS. 21A-21H).

Referring to FIGS. 4-16, the upper connector member (31) preferablyincludes a shoulder (92) on the bottom surface thereof for location ofthe lower connector member (33). The lower connector member (33) alsoincludes a shoulder 96 that is constructed and arranged to cooperatewith shoulder (92) to maintain alignment of the two components. Thelower connector member (33) includes a substantially spherical shapedlower receptacle (38) housing a lower split retainer ring (40) and upperretainer ring (42). The retainer rings (40, 42) are placed within thelower receptacle (38) during the manufacturing process. The shoulders(92) and (96) are utilized to align the components, and the upper andlower connector members are then laser welded together to preventdislodgement of the retainer rings after assembly. It should be notedthat other suitable methods or techniques of attaching the upper andlower connector members together may be utilized without departing fromthe scope of the invention, such methods may include, but should not belimited to spot welding, threads, adhesives, pins swaging, solder,interference fits and suitable combinations thereof.

Referring to FIGS. 5-13 and 17-18, the upper retainer ring (42) isillustrated. The upper retaining ring (42) is positioned within thelower receptacle (38) with an upper edge (52) positionable within thecavity formed by side wall (41); the upper retaining ring side wall (43)cooperates with side wall (41) of the cavity to prevent rotation of theupper retaining ring. The inner surface (56) of the upper retaining ringprovides for self centering by engaging of the outer surface of thespherical connector (18). The upper surface (53) of the upper retainingring (104) preferably includes a concave cylindrical surface forcooperation with the connecting rod (70). The cylindrical surfaceprovides additional surface area for contact with the connecting rod andmay include a knurled or otherwise modified surface finish adapted toenhance gripping power between the rod and the connecting assembly (30).One embodiment of the upper retaining ring (42) includes spring pockets(98) that are located to cooperate with spring pockets (100) (FIG. 11)positioned in the upper connector member to locate and contain coilsprings (102)(FIG. 5). The spring members bias the upper retaining ringtoward the opening (50) of the lower receptacle.

Referring to FIGS. 19-21H, assembly of the locking polyaxial ball andsocket fastener is illustrated. Prior to assembly, the bone anchor 12may be inserted into bone in a normal fashion without the connectormember attached thereto. This allows the physician to a clearvisualization of the screw as it is rotated into the bone. Afterinsertion of the bone screw, the spherical connector (18) of the boneanchor (12) is inserted through the opening (50) (FIG. 21A) wherein thespherical connector (18) contacts the lower retainer ring (40). Thelower retaining ring is pushed into contact with the upper retainingring (FIG. 21B) thereby collapsing the springs 102 to cause the lowerretaining ring to contact the ramps 94 (FIG. 21C). The cooperation ofthe ramps with the upper surface of the lower retaining ring causes thelower retaining ring to open up in diameter to snap over the majordiameter (d) of the ball (FIGS. 21D-21F). Once the lower ring is openedsufficiently, the springs (102) move the ring to the lower portion ofthe lower receptacle thereby preventing the ball from being removed fromthe lower receptacle while still allowing polyaxial movement of theconnector assembly with respect to the screw (FIGS. 21G-21H). Lockingthe ball and socket connection into a desired position is thereafteraccomplished by placing a connecting rod (70) into the connectorassembly so that it contacts the upper surface (53) of the upperretaining ring. A securing element in the form of a set screw (80) isinserted into the threaded portion of the upper retaining member untilthe set screw contacts the rod (70), causing the rod to move the upperretaining ring into contact with the spherical ball (18). The movementcauses the ball to move toward the opening (50), wedging the lower splitretaining ring 40 between the inner surface (120) (FIG. 14) of the lowerretaining ring and the ball, locking the assembly in a desired position.It should be appreciated that this construction provides two rings ofcontact between the connector assembly and the spherical ball. The firstring of contact is provided by the upper retaining ring (42) and thesecond ring of contact is provided by the lower retaining ring (40). Itshould be noted that while the springs (102) are illustrated as coilsprings, any spring or resilient type member suitable for displacing thesplit retaining ring may be utilized without departing from the scope ofthe invention. Such spring or resilient members may include, but shouldnot be limited to, Belleville type springs, leaf springs, polymericmembers and suitable combinations thereof.

Unique to this invention is the ability for the surgeon to attachvarious types of bone anchors or the like to the connecting assembly.While there is a myriad of anchoring devices that can be adapted toinclude the spherical ball, bone hooks etc., for ease of illustrationthe bone screw is depicted and it is well known that various lengths anddiameters of bone screws are available, many of which would not fitthrough the inner diameter of the connector assembly. Thread styles,lengths and so forth the best suited for installation may be estimatedbefore surgery but it is well known that only during actual surgery canthe proper style be confirmed. Because it is most difficult to predictthe proper combination of anchor screw and connector member, surgeonsmust either have a large selection of spinal implants to choose from orbe forced to use the closest combination and hope that it will suffice.

It should be noted that while various types of bone screws have beenmentioned, the instant installation allows placement of an anchoringdevice having a spherical connector into position before a connectormember is attached. This provides the surgeon with an option ofpositioning the bone screw before placement of the connecting memberthereby providing a simplified installation should positioning of theanchoring screw be difficult due to muscle or other interference.Installation of a bone screw with the connecting member allows a rangeof mobility as well as better visual positioning. Further, while theU-shaped connector member is depicted, various types of connectormembers may be used in combination with the spherical connector (18)allowing a surgeon to select the appropriate combination during surgerythereby enhancing the success for the benefit of the patient as well aslowering cost of inventory necessary when estimating the various typesof situations that the surgeon may encounter during the operation.

It should also be noted that while only the lower retaining ring isillustrated as being split, the upper ring may also be split tofacilitate placement into the lower receptacle without the need to weldthe upper and lower portions of the retainer assembly together.

Referring to FIG. 19, the outer surface (83) of the spherical connector(18) may include a ridged style surface for enhanced frictionalengagement. It should also be noted that the spherical connector ispreferably sized only for insertion through the bottom opening (50) ofthe connector assembly and would not fit through the connector memberopening (80) even if the upper retainer ring (42) was removed. Thisentry is a departure from conventional prior art which typically placesthe shank of a bone screw through the connector member wherein theopening along the bottom of the connector is sized to prevent passage ofthe spherical connector.

Referring to FIGS. 4 and 19, the fastener receptacle (22) can be made ofvarious shapes with the emphasis of providing a shank or a conventionalfastener tool that provides the greatest amount of torque with minimalamount of slippage during installation. The inner surface (54)(FIGS.15-16) of the lower retainer ring (40) is shown with a minimal portionof the surface engaging the spherical connector (18) duringinstallation. However, once the spherical connector is positioned, themajority of the inner surface (54) of the lower split retaining ring(40) will engage the spherical connector (18) for optimal frictionengagement. Similarly, the inner surface (56) of the upper retainer ring(42) (FIG. 18) engages the spherical connector (18) for frictionalengagement. Preferably the inner surfaces (54 and 56) include a ridgedsurface that cooperates with the ridged surface (83) of the sphericalconnector (18).

Referring to FIGS. 22-25, an alternative embodiment of the instantinvention is illustrated. In this embodiment, the set screw (80) isreplaced by a threaded nut (110). The threaded nut includes internalhelical threads constructed and arranged to cooperate with externalthreads (112) formed on the outer surface of the upper connector member(31). The threaded nut (110) includes a bottom surface (114) thatengages the rod member (70), thereby causing the upper retainer member(42) to engage the spherical connector (18) to wedge the lower retainingring (40) between the spherical connector and the inner surface (120) ofthe lower connector member (33) to lock the position of the sphericalconnector with respect to the connector assembly.

Referring to FIGS. 26-30, an alternative embodiment of the instantinvention is illustrated having mono-axial movement (see FIG. 26) inplace of the polyaxial movement of the embodiments described above. Boneanchors that provide mono-axial movement, e.g. along a single axis,instead of polyaxial movement, e.g. motion along several different axes,are often desired for certain types of the spinal ailments such as, butnot limited to, scoliosis. To limit the movement of the ball and socketfastener to a single axis, the spherical connector (18) includes, atleast one, and more preferably a pair of guide(s) surface(s) (116)positioned on opposite side sides of the spherical connector (18)(FIG.27). The guide surfaces (116) cooperate with rails 118 positioned withinthe inner surface (56) of the upper retaining ring (42). The rails (118)and the guide surfaces (116) cooperate to prevent substantial rotationof the spherical connector (18) while allowing movement of the boneanchor (12) along a single axis (FIG. 26).

All patents and publications mentioned in this specification areindicative of the levels of those skilled in the art to which theinvention pertains. All patents and publications are herein incorporatedby reference to the same extent as if each individual publication wasspecifically and individually indicated to be incorporated by reference.

It is to be understood that while a certain form of the invention isillustrated, it is not to be limited to the specific form or arrangementherein described and shown. It will be apparent to those skilled in theart that various changes may be made without departing from the scope ofthe invention and the invention is not to be considered limited to whatis shown and described in the specification and any drawings/figuresincluded herein.

One skilled in the art will readily appreciate that the presentinvention is well adapted to carry out the objectives and obtain theends and advantages mentioned, as well as those inherent therein. Theembodiments, methods, procedures and techniques described herein arepresently representative of the preferred embodiments, are intended tobe exemplary and are not intended as limitations on the scope. Changestherein and other uses will occur to those skilled in the art which areencompassed within the spirit of the invention and are defined by thescope of the appended claims. Although the invention has been describedin connection with specific preferred embodiments, it should beunderstood that the invention as claimed should not be unduly limited tosuch specific embodiments. Indeed, various modifications of thedescribed modes for carrying out the invention which are obvious tothose skilled in the art are intended to be within the scope of thefollowing claims.

1. A ball and socket fastener comprising: an anchoring member having ashank and a spherical connector; a connecting assembly having a socketconstructed and arranged for receipt of said spherical connector along afirst end and a securing element securable to a second end, an upperretainer ring disposed within said socket and positionable along anupper surface of said spherical connector, a lower retainer ringdisposed within said socket and positionable along a lower surface ofsaid spherical connector so that said connecting assembly movespolyaxially with respect to said anchoring member, said securing elementtraversable between an unlocked position and a locked position forcontrolling said polyaxial movement; wherein said spherical connectorhead is received through said first end and positioned between saidupper and said lower retainer rings.
 2. The ball and socket fastener ofclaim 1 wherein said lower retainer ring includes a split to allow saidlower retainer ring to expand in diameter.
 3. The ball and socketfastener of claim 2 wherein said connecting assembly includes at leastone ramp surface positioned to cooperate with said lower retainer ringduring securement of said spherical connector to said socket to expandsaid lower retaining ring to pass a major diameter of said sphericalconnector.
 4. The ball and socket fastener of claim 1 wherein saidconnecting assembly includes a substantially U-shaped opening sized toaccept a rod member, an upper surface of said retaining ring including arod engaging surface extending into said U-shaped opening, wherein saidlocked position of said securing element traverses said upper retainerring to frictionally engage said spherical connector.
 5. The ball andsocket fastener of claim 4 wherein said upper retaining ring includes acylindrically concave upper surface for cooperation with a connectingrod member.
 6. The ball and socket fastener of claim 4 wherein saidlocked position causes said lower retaining ring to engage an innersurface of said connector and said lower portion of said sphericalconnector to immobilize said spherical connector.
 7. The ball and socketfastener of claim 1 wherein said shank includes at least one helicalthread.
 8. The ball and socket fastener of claim 1 wherein said secondend of said connecting assembly includes an internal thread and saidcompression element is further defined as a set screw.
 9. The ball andsocket fastener of claim 1 wherein said second end of said connectingassembly includes an external thread and said compression element isfurther defined as a nut having internal threads.
 10. The ball andsocket fastener of claim 1 including a biasing member positioned betweensaid upper retaining ring and said lower retaining ring.
 11. A ball andsocket fastener comprising: an anchoring member having a shank and aspherical connector, said spherical connector including at least oneguide surface; a connecting assembly having a socket constructed andarranged for receipt of said spherical connector along a first end and asecuring element securable to a second end, an upper retainer ringdisposed within said socket and positionable along an upper surface ofsaid spherical connector, said upper retaining ring including at leastone rail positioned to cooperate with said at least one guide surface, alower retainer ring disposed within said socket and positionable along alower surface of said spherical connector, said at least one guidesurface and said at least one rail cooperating so that said connectingassembly moves mono-axially with respect to said anchoring member, saidsecuring element traversable between an unlocked position and a lockedposition for controlling said mono-axial movement; wherein saidspherical connector head is received through said first end andpositioned between said upper and said lower retainer rings.
 12. Theball and socket fastener of claim 11 wherein said lower retainer ringincludes a split to allow said lower retainer ring to expand indiameter.
 13. The ball and socket fastener of claim 11 wherein saidconnecting assembly includes at least one ramp surface positioned tocooperate with said lower retainer ring during securement of saidspherical connector to said socket to expand said lower retaining ringto pass a major diameter of said spherical connector.
 14. The ball andsocket fastener of claim 11 wherein said connecting assembly includes asubstantially U-shaped opening sized to accept a rod member, an uppersurface of said retaining ring including a rod engaging surfaceextending into said U-shaped opening, wherein said locked position ofsaid securing element traverses said upper retainer ring to frictionallyengage said spherical connector.
 15. The ball and socket fastener ofclaim 14 wherein said upper retaining ring includes a cylindricallyconcave upper surface for cooperation with a connecting rod member. 16.The ball and socket fastener of claim 14 wherein said locked positioncauses said lower retaining ring to engage an inner surface of saidconnector and said lower portion of said spherical connector toimmobilize said spherical connector.
 17. The ball and socket fastener ofclaim 11 wherein said shank includes at least one helical thread. 18.The ball and socket fastener of claim 11 wherein said second end of saidconnecting assembly includes an internal thread and said compressionelement is further defined as a set screw.
 19. The ball and socketfastener of claim 11 wherein said second end of said connecting assemblyincludes an external thread and said compression element is furtherdefined as a nut having internal threads.
 20. The ball and socketfastener of claim 11 including a biasing member positioned between saidupper retaining ring and said lower retaining ring.
 21. A polyaxial balland socket joint that can be locked into a fixed position comprising: abone screw having threads on one end for use in anchoring to the spineand a spherical connector on the other end operating as a pivot pointabout which a connecting assembly is movable in a polyaxial fashion,said connecting assembly having a substantially U-shape and including alower receptacle that operates as a socket for housing an upper retainerring and a lower split retaining ring, said socket receptive to saidspherical connector which is inserted through said lower split retainerring causing a momentary displacement thereof which allows for thepositioning of said spherical connector between said upper and saidlower retainer rings.